I would go for an H21* and get a H24* so you can drop both the 3 and 4 irons.
I have a 3 and a 4..but my 4 has a slightly higher loft? I would reccomend going out and demoing a few to get a feel for where the gap would exisit betweeen your 3iron and 4H or your 3H and 4i.